DE102014211108A1 - Refrigerating appliance with hot gas defrosting and defrosting - Google Patents

Abstract

A refrigerator, in particular domestic refrigeration appliance, comprises at least one storage chamber (2), an evaporator (3) for cooling the storage chamber (2), a compressor (7) for driving a refrigerant flow through the evaporator (3) and a control unit (17) is set to power the compressor (7) and to switch between a normal cooling mode in which refrigerant passes on the way from the compressor (7) to the evaporator (3) a throttle point (12), and a defrost mode in which the refrigerant Bypassing of the throttle point (12) from the compressor (7) to the evaporator (3) passes. The control unit (17) is further switchable between a drive operation mode in which a current supplied to the compressor (7) by the control unit (17) causes a refrigerant flow driving movement of the compressor (7), and a heating operation mode in which The compressor (7) energized without causing movement of the refrigerant.

Description

The present invention relates to a refrigerator, in particular a domestic refrigerator such as a refrigerator or freezer, in which an evaporator can be deflated by passing warm refrigerant, and a method for defrosting the evaporator in such a refrigerator.

The defrosting of an evaporator by passing warm refrigerant is common in large refrigeration systems. It allows for energy-efficient defrosting, since the gas passed through it releases its heat predominantly at the coldest points of the evaporator, so that when the evaporator has iced and ice-free areas, the heat is given off mainly at the icy areas and unnecessary heating of already defrosted parts the evaporator can be largely avoided. For domestic refrigeration appliances, hot gas defrosting is not widespread because the waste heat from the high efficiency compressors installed in these appliances is generally insufficient to carry out a defrosting operation within a reasonable time, without excessive heating of the refrigerated product stored in the refrigerator, and because of faster defrosting necessary installation of a heater for heating the refrigerant causes additional costs that make such refrigerators unattractive to consumers.

Object of the present invention is to provide a refrigeration device, which is despite high energy efficiency of its compressor with minimal cost in a position to provide sufficient hot gas for a rapid defrosting, or specify a cost-implementable and efficient defrosting.

The object is achieved on the one hand, by a compressor, in particular a household refrigerator, with at least one storage chamber, an evaporator for cooling the storage chamber, a compressor for driving a refrigerant flow through the evaporator and a control unit which is configured to power the compressor supply and switch between a normal cooling mode in which refrigerant passes a throttle point on the way from the compressor to the evaporator, and a defrost mode in which the refrigerant, bypassing the throttle - and thus absent the otherwise occurring there cooling - passes to the evaporator, the control unit between a driving operation mode in which a flow supplied to the compressor by the control unit causes a movement of the compressor driving the refrigerant flow, and a heating operation mode in which it energizes the compressor without moving the K to cause elimination. The electrical power fed into the compressor in heating mode can only be released as heat in the compressor, so that when refrigerant is recirculated from the compressor following the heating mode of operation, it will absorb the heat from the compressor and transport it to the evaporator.

In order to be able to bypass the throttle, a refrigerant circuit of the refrigerator should include a shunt line connecting an output of the compressor to an inlet of the evaporator parallel to the choke point, and a shut-off valve located in the shunt line should be closed in the normal cooling mode and open in the defrost mode.

Another shut-off valve connected in series with the restriction and the evaporator may be closed in defrost mode to completely force the refrigerant onto the bypass line; However, this second shut-off valve is not absolutely necessary because, even if it is missing or open, the small cross section of the throttle is sufficient to direct the refrigerant over the shunt line predominantly.

The control unit should be set to temporarily activate the heating operation mode before transitioning to the defrosting mode to achieve a high temperature of the refrigerant circulating in the evaporator in the defrosting mode, and thus a quick defrosting operation.

If necessary, if the available amount of heat for a fast defrost is not sufficient, can be switched back from the defrost mode temporarily in the heating operation mode; however, it is preferable to manage with a single heating operation phase before the start of the defrost mode, since at the beginning of the defrost mode, when the evaporator is frosted over a large area, the evaporator for the most part can not heat above 0 ° C, even though the refrigerant pumped through is considerably warmer, whereas in later stages of defrosting, when the evaporator is partially ice-free, a high refrigerant temperature may result in unnecessary heating of these ice-free areas. Therefore, it is advantageous for an energy-efficient defrosting operation when the temperature of the refrigerant is high at the transition to the defrost mode and decreases during the defrosting mode.

In the simplest case, the control unit can be set up to activate the heating operating mode before each transition into the defrosting mode. In order to further reduce the energy consumption during defrosting, however, the heating operating mode can also be linked to conditions. For example, the control unit may be configured to activate the heating operation mode only if before the transition in the defrost mode, the temperature of the compressor is below a limit. To detect this temperature, the control unit should be connected to a temperature sensor on the compressor; As such a temperature sensor may serve a PTC element, which is conventionally present in many compressors to interrupt the operation of the compressor in case of overheating.

A low ambient temperature results in short periods of operation of the compressor, which are interrupted by long standstill phases, so that at low ambient temperatures there is a high probability that the compressor temperature is low and the compressor can not supply the amount of heat required for a defrosting operation. Therefore, the control unit may also be connected to an ambient temperature sensor to activate the heating mode of operation when the ambient temperature is below a threshold prior to the transition to the defrost mode.

As a drive unit, the compressor may have an asynchronous motor. In some types of electric motors, especially in asynchronous motors, the energizing of a main winding is not sufficient to initiate a rotation, and it is an auxiliary winding needed to deflect when starting the engine from an equilibrium position and specify its direction of rotation. When in the heating mode, the auxiliary winding remains de-energized and consequently no direction of rotation is given, strong currents can be fed into the main winding and heat them up, without the rotation of the motor is started.

Instead of leaving the auxiliary winding in the heating mode completely energized, can also be provided that it is continuously energized by the control unit, so as to use the auxiliary winding for heat generation.

In order to selectively suppress or maintain the energization of the auxiliary winding, a switch controlled by the control unit may be connected in series with the auxiliary winding.

Alternatively and in a manner known per se, a PTC element may be connected in series with the auxiliary winding in order to enable a current flow in the auxiliary winding, which is required for starting the rotation, when the motor is still cold when the PTC element is still cold but after a short time, as a result of the heating caused by the current flow of the PTC element, turn off or to reduce a not significantly affecting the movement of the motor current. In such a motor with a PTC element, the control unit may be configured to turn on the heating operation mode by first energizing the motor in the manner conventional for starting the engine to thereby heat the PTC element, then momentarily interrupting the energization that a possibly started movement of the motor can come to a standstill, and then resumes the energization, so that although the main winding is supplied with power and generates heat, in the absence of a significant current flow in the auxiliary winding of the engine, however, remains at a standstill.

A start of the compressor can also be prevented by the fact that at the outlet of the compressor is too high pressure against which the compressor has to work. Therefore, regardless of the type of engine, it is also possible to activate the heating operation mode by operating the compressor for a short time to build up at its output a pressure high enough to stop when the compressor has been stopped for a short time prevent restarting.

• a) Betreiben des Verdichters in einem Heizbetriebsmodus, in dem der Verdichter mit Strom beaufschlagt wird, ohne eine Bewegung von Kältemittel anzutreiben, dann
• b) Betreiben des Verdichters in einem Antriebsbetriebsmodus, in dem das das Kältemittel vom Verdichter unter Umgehung der Drosselstelle zum Verdampfer befördert wird.

The object is further achieved by a method for defrosting an evaporator, which can be acted upon by a compressor via a throttle point in a normal cooling mode with refrigerant, comprising the steps:

• a) operating the compressor in a heating mode of operation in which the compressor is energized without driving a movement of refrigerant, then
• b) operating the compressor in a drive mode of operation, in which the refrigerant is conveyed from the compressor, bypassing the throttle point to the evaporator.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures.

Show it:

1 a schematic representation of a household refrigerator according to the invention;

2 a block diagram of a control unit and a compressor motor of the refrigerator according to a first embodiment;

3 one too 2 analog block diagram according to a second embodiment of the invention; and

4 one too 2 analog block diagram according to a third embodiment of the invention.

This in 1 Household refrigeration appliance shown schematically comprises a heat-insulating housing 1 in which at least one storage chamber 2 is formed for refrigerated goods. An evaporator 3 for cooling the storage chamber 2 is typically in one of the storage chamber 2 separated evaporator chamber 4 housed and cools the storage chamber 2 by placing air between storage chamber 2 and evaporator chamber 4 by means of a fan 5 is circulated.

An outlet of the evaporator 3 is via a suction line 6 with a suction connection of a compressor 7 connected. A pressure line 8th runs from an outlet of the compressor 7 over a branch 9 , a liquefier 10 and a shut-off valve 11 to one as a throttle point 12 acting capillary. At a low pressure line section 13 between the throttle point 12 and the evaporator 3 is a confluence 14 with one of the branch 9 outgoing shunt line 15 intended. In the shunt line 15 is a second shut-off valve 16 arranged.

The shut-off valves 11 . 16 , the ventilator 5 and the compressor 7 are controlled by an electronic control unit 17 , In known manner, the control unit 17 with a temperature sensor 18 at the storage room 2 connected to decide if the storage room 2 Cooling demand has or not and in the presence of cooling demand the compressor 7 operate in a normal cooling mode, in which the compressor 17 Refrigerant from the evaporator 3 sucks and under high pressure to the condenser 10 outputs. In this normal cooling mode is the shut-off valve 11 open to liquid refrigerant from the condenser 10 over the throttle point 12 in the evaporator 3 let in the shut-off valve 16 is closed, and the fan 5 is in operation to the evaporator 3 cooled air in the storage chamber 2 to distribute.

During the normal cooling mode, frost will hit the evaporator 3 down, the heat exchange with the through the evaporator chamber 4 slows circulating air and thus affects the efficiency of the refrigerator. The control unit 17 is set up, the amount of frost on the evaporator 3 If this is large enough to significantly affect the heat exchange, defrost the evaporator 3 in the way. The amount of frost on the evaporator 3 can be estimated in different ways. A simple method to follow captures the control unit 17 the duration of successive phases in the normal cooling mode and determines the need for defrosting when the accumulated duration of these phases has exceeded a predetermined limit.

Because every time you open a door of the housing 1 moist outside air into the storage chamber 2 passes, it can be assumed that the amount of frost on the evaporator 3 is associated with the number of door openings made since the last defrost, and the need for defrosting can be detected by another method if this number exceeds a predetermined value.

More direct methods for detecting the frost on the evaporator 3 For example, on a time delay between the beginning of the normal cooling mode and a resulting, from the temperature sensor 18 recorded cooling of the storage chamber 2 or on the change of a resonant frequency of the evaporator 3 are based on the frost adhering to it.

If the control unit 17 As a result of the simple deficiency of the defrosting operation, it can unconditionally switch first to a heating operation mode before starting the defrosting operation of the compressor 7 stop; However, the decision as to whether such a heating is required, but can also be done taking into account operating conditions of the refrigerator. For example, a second temperature sensor 19 be provided to detect the temperature in the vicinity of the refrigerator. If this is above a limit, it can be assumed that before the present time the compressor 7 has run long enough to contain the amount of heat needed for defrosting, so that in such a case, the energy-intensive heating operation mode is not needed before the start of defrosting. Alternatively, the temperature sensor could 19 also directly on the compressor 7 be arranged to measure its temperature and thus estimate the amount of heat stored in it directly. A simpler variant to consequence of the temperature sensor 19 also omitted, and the control unit 17 decides whether the amount of heat in the compressor on the basis of the already measured duration of the immediately preceding normal cooling phase as described above 7 is sufficient for a defrost.

In heating mode, the control unit powers 17 the compressor 7 Although with power, but rotates the motor of the compressor 7 not, so that the supplied electrical energy in the compressor 7 is completely converted into heat. Depending on the design of the compressor 7 can there be different ways of energizing this without the motor rotating; Some of these options will be discussed in detail later.

To subsequently switch to the defrost mode, the control unit closes 17 the shut-off valve 11 , opens the shut-off valve 16 and puts the engine of the compressor 7 in progress, leaving the compressor 7 Refrigerant circulates. That in the compressor 7 heated refrigerant reaches over the Shunt line 15 the evaporator 7 , where it gives off its heat and flows to the compressor 7 back.

The duration of the defrost mode can be fixed, preferably variable as needed. To achieve such a demand-dependent variability, z. B. the amount of frost on the evaporator 3 by their influence on the resonant frequency of the evaporator 3 be estimated, or there may be a temperature sensor on the suction line 6 or in the evaporator chamber 4 be provided to a temperature increase of the effluent from the evaporator refrigerant or the temperature in the evaporator chamber 4 to conclude that the hoop has completely thawed, and then exit the defrost mode.

2 shows in a block diagram the control unit 17 and the one controlled by her, here with 20 designated motor of the compressor 7 according to a first embodiment. The control unit 17 is here divided into a logic unit 21 which, as described above, the operating mode of the compressor 7 - Normal cooling mode, defrost mode, heating mode or sleep mode - sets and the valves 11 . 16 as well as the fan 5 controls, a relay 22 and an inverter 23 , The motor 20 is a known asynchronous motor with one in three strands 25 articulated main winding 24 on the stator and an auxiliary winding 26 , each at a start of the engine 20 is energized to initiate the rotation and determine its direction.

The logic unit 21 may have different methods of controlling the relay 22 and the inverter 23 deploy. A first of these procedures results in the relay 22 during the heating mode, so that the auxiliary winding 26 remains de-energized, whereas the inverter 23 the main winding 24 energized. The order in which the inverter 23 the individual strands 25 the stator winding 24 powered, may be the same as in normal cooling mode. As a trigger of the rotation of the rotor triggering on the auxiliary winding 26 missing, comes a turn of the compressor 7 still not working during the heating mode, and the whole into the main winding 24 fed electrical power only leads to their heating.

A second method results in the logic unit 21 the relay 22 closed during the heating mode, allowing a continuous current through the auxiliary winding 26 flows, in addition to generating heat in the engine 20 contributes. In this procedure, the order in which the inverter should 23 the strands 25 energized, under the control of the logic unit 21 be variable to ensure that an order suitable for driving a rotation of the motor is generated only during the normal cooling mode, and so exclude that in the heating operation mode, a rotation is initiated. For this purpose, for example, the strands 25 be subjected to DC voltage, so that no rotating magnetic field in the engine 20 arises, or the order of the at the terminals U, V, W of the inverter 23 output current pulses can be selected so that the direction of rotation of the resulting magnetic field in the engine 20 changes faster than the rotor can follow.

If the engine 20 energized at standstill, significantly higher currents occur in the main winding than when the motor 20 rotates in normal operation. The resulting warming, if too long, can destroy the engine 20 to lead. To avoid this, conventional compressors usually have an overheating protection, for example in the form of a PTC or bimetallic element, which at too high a temperature of the motor 20 its power supply interrupts. Such an overheating protection element 27 as shown also on the compressor 7 be provided; the temperature at which it takes effect is lower than the temperature of the compressor required for defrosting 7 so it does not obstruct the defrost.

In the embodiment of 3 controls the logic unit 21 via a relay 28 the supply of both the inverter 23 as well as a series connection of a PTC element 29 and the auxiliary winding 26 with operating voltage. The inverter 23 produced at its three with the strands 25 connected output terminals U, V, W one for driving a rotation of the motor 20 suitable pulse sequence, as long as the supply voltage is applied. If the compressor 7 has been off long enough to cool the PTC element 29 to allow, and the control unit 17 the relay 28 therefore, the inverter starts 23 to work, and at the same time a current flows through the PTC element 29 and the auxiliary winding 26 , allowing a rotation of the motor 20 gets underway. The PTC element 29 is heated by the current flowing through it, so that its resistance increases rapidly after a short time and the current flow through the auxiliary winding 26 is so severely restricted that the magnetic field of the auxiliary winding 26 on the operation of the engine 20 has no influence.

To initiate a heating operation phase, the logic unit opens 21 the relay 28 again for a short time, typically a few seconds, around the engine 20 to come to a standstill. This short time is not enough for the PTC element 29 Allow to cool so far that again a significant flow of current through the auxiliary winding 26 is possible. If after interruption the relay 28 is closed again, therefore, although the main winding 24 from the inverter 23 energized, but again lacks the impetus on the auxiliary winding 26 , which is a rotation of the engine 20 would put that into the main winding 24 fed electrical power only leads to heating.

If in this way the compressor 7 heated enough to allow a quick defrost, opens the logic unit 21 the relay 28 again, this time long enough to also cool the PTC element 29 allow, so if the relay 28 is closed again, also on the auxiliary winding 26 Electricity flows and the rotation of the engine 20 gets underway.

4 shows a variant in which the logic unit 21 two relays controls, one relay 28 that the inverter 23 supplied with operating voltage, and a relay 30 that the series circuit of auxiliary winding 26 and PTC element 29 optionally with the operating voltage or with a source 31 a measuring voltage that is considerably lower than the operating voltage. To set the heating mode, the logic unit closes 21 first the relay 28 and acts on the PTC element 29 and the auxiliary winding 26 with the low measuring voltage, which is used to start the rotation of the motor 20 not enough. By measuring the current in the PTC element 29 using a measuring instrument 32 monitors the logic unit 21 the heating of the engine 20 and terminates the heating operation mode when a temperature sufficient for defrosting is reached, ie, the PTC element 29 acts here as the above-mentioned temperature sensor 19 on the evaporator 7 ,

The temperature sufficient for defrosting is significantly lower than that of the PTC element 29 if it is over the relay 30 is acted upon by the operating voltage. Therefore, it is sufficient here to switch from heating mode to defrost the relay 30 switch, so the auxiliary winding 26 and the PTC element 29 be connected to the operating voltage and a surge across the auxiliary winding 26 comes about, the rotation of the engine 20 starts.

As described above, can control over whether a current to the motor 20 initiates a rotation or not, with an auxiliary winding 26 Asynchronous motor via the control of the auxiliary winding 26 be exercised. Regardless of the type of compressor 7 used engine 20 can also be a strong pressure difference between pressure line 8th and suction line 6 a start of the engine 20 prevent. Therefore, in such a case, the control unit 17 bring about a heating mode of operation in which the compressor 7 , possibly with closed shut-off valves 11 and 16 , running short time in the pressure line 8th build up a high pressure, then the compressor 7 for a short time shuts off to the engine 20 to let go to rest. If subsequently the control unit 17 the engine 20 at still closed valves 11 . 16 energized again prevents the high pressure on the line 8th a start of the engine 20 , In such a case, it suffices that the control unit 17 the shut-off valve 16 opens, so that the engine 20 starts and the unit goes from the heating operation phase into the defrosting phase.

LIST OF REFERENCE NUMBERS

1

 casing

2

 storage chamber

3

 Evaporator

4

 evaporator chamber

5

 fan

6

 suction

7

 compressor

8th

 pressure line

9

 branch

10

 condenser

11

 shut-off valve

12

 restriction

13

 Low-pressure line section

14

 confluence

15

 Shunt line

16

 shut-off valve

17

 control unit

18

 temperature sensor

19

 temperature sensor

20

 engine

21

 logic unit

22

 relay

23

 inverter

24

 main winding

25

 strand

26

 auxiliary winding

27

 Overheating protection element

28

 relay

29

 PTC element

30

 relay

31

 Measuring voltage source

32

 gauge

Claims (15)

Refrigerating appliance, in particular household refrigerating appliance, with at least one storage chamber ( 2 ), an evaporator ( 3 ) for cooling the storage chamber ( 2 ), a compressor ( 7 ) for driving a refrigerant flow through the evaporator ( 3 ) and a control unit ( 17 ), which is set up the compressor ( 7 ) and between a normal cooling mode, in which refrigerant on the way from the compressor ( 7 ) to the evaporator ( 3 ) a throttle point ( 12 ), and to switch to a defrost mode in which the refrigerant, bypassing the throttle point ( 12 ) from the compressor ( 7 ) to the evaporator ( 3 ) characterized in that the control unit ( 17 ) between a drive mode of operation, in which a current to which the control unit ( 17 ) the compressor ( 7 ), a refrigerant flow driving movement of the compressor ( 7 ), and is switchable to a heating operation mode in which the compressor ( 7 ) is energized without causing movement of the refrigerant. Refrigerating appliance according to claim 1, characterized in that the power consumption of the compressor ( 7 ) in the heating mode is at least as high as in the drive mode of operation. Refrigerating appliance according to claim 1 or 2, characterized in that a refrigerant circuit a shunt line ( 15 ) parallel to the throttle point ( 12 ) an output of the compressor ( 7 ) with an input of the evaporator ( 3 ) and that one in the shunt line ( 15 ) arranged shut-off valve ( 16 ) is closed in normal cooling mode and open in defrost mode. Refrigerating appliance according to claim 1, 2 or 3, characterized in that the control unit ( 17 ) is set to temporarily activate the heating operation mode before transitioning to the defrosting mode. Refrigerating appliance according to claim 4, characterized in that the control unit ( 17 ) is set to activate the heating mode if, prior to the transition to the defrost mode, the temperature of the compressor ( 7 ) is below a threshold; or - the ambient temperature is below a limit; or - the duration of the last phase in the drive operating mode is below a limit. Refrigerating appliance according to one of claims 1 to 5, characterized in that the compressor ( 7 ) has an asynchronous motor. Refrigerating appliance according to one of claims 1 to 6, characterized in that a motor ( 20 ) of the compressor ( 7 ) a main winding energized in the drive mode of operation ( 24 ) and an auxiliary winding energized only at the beginning of the drive operating mode (FIG. 26 ) and that in the heating mode, the auxiliary winding ( 26 ) remains energized. Refrigerating appliance according to one of claims 1 to 6, characterized in that a motor ( 20 ) of the compressor ( 7 ) a main winding energized in the drive mode of operation ( 24 ) and an auxiliary winding energized only at the beginning of the drive operating mode (FIG. 26 ) and that in the heating mode, the auxiliary winding ( 26 ) is continuously energized. Refrigerating appliance according to claim 7 or 8, characterized in that a by the control unit ( 17 ) controlled switch ( 28 ; 30 ) with the auxiliary winding ( 26 ) is connected in series. Refrigerating appliance according to one of claims 1 to 6, characterized in that a motor ( 20 ) of the compressor, a main winding ( 24 ) and parallel to the main winding ( 24 ) one with a PTC element ( 29 ) Auxiliary winding connected in series ( 26 ) and that the control unit ( 17 ) is set to switch on the heating mode by turning off the engine ( 20 ) is energized to the PTC element ( 29 ), the current is interrupted and resumed. Refrigerating appliance according to one of the preceding claims, characterized in that the compressor ( 7 ) is capable of generating at its output a pressure against which a start-up of the compressor ( 7 ) is not possible, and that the control unit ( 17 ) is set to activate the heating mode by moving the compressor ( 7 ) temporarily stops and then energizes it again, before the pressure at its output has dropped to a value at which startup is possible. Refrigerating appliance according to one of claims 1 to 11, characterized in that the control unit ( 17 ) an inverter ( 23 ). Refrigerating appliance according to one of the preceding claims, characterized in that the compressor ( 7 ) has at least three terminals (U, V, W) to be energized in a first order to prevent rotation of the compressor ( 7 ) in one working direction, and that the control unit ( 17 ) is set up in the heating operation mode to energize the terminals (U, V, W) in a different order from the first order second order. Refrigerating appliance according to claim 13, characterized in that winding strands ( 25 ) of an engine ( 20 ) of the compressor ( 7 ) are connected to the connection terminals (U, V, W) in such a way that, when the terminals (U, V, W) are energized, they generate a magnetic field which rotates in a first direction of rotation, and that the second order is chosen that a rotating magnetic field with a rotating sense of rotation, a stationary or an oscillating magnetic field is generated. Method for defrosting an evaporator ( 3 ), which in a normal cooling mode of a compressor ( 7 ) via a throttle point ( 12 ) can be acted upon with the refrigerant, comprising the steps of: a) operating the compressor ( 7 ) in a heating mode of operation in which the compressor ( 7 ) is energized without driving a movement of refrigerant, then b) operating the compressor ( 7 ) in a drive mode of operation in which the refrigerant from the compressor ( 7 ) bypassing the restriction ( 12 ) to the evaporator ( 3 ).

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